1. Field of the Invention
The present invention relates to a weatherstrip that is used as an automotive part.
2. Related Background of the Invention
The weatherstrip attached to the window frames of automobile doors is an automotive part that seals the outer periphery of the window glass. The weatherstrip thereby holds the window glass securely in place, prevents rain, wind, dust, and so forth from getting into the passenger compartment, and allows the window glass to be opened and closed more smoothly. The weatherstrip is usually made of an elastomeric material so that it can function as intended. More specifically, it is made of ethylene-propylene-diene rubber (EPDM), polyolefin thermoplastic elastomer (TPO), or the like.
An example of prior art related to weatherstrips is a product of using a urethane- or silicone-based surface treatment agent to coat surfaces that come into contact with window glass, and curing the agent to obtain coating layer. Another example is a weatherstrip molded from a specific thermoplastic elastomer or resin.
For example, Japanese Patent Publication H7-73893 discloses a weatherstrip in which portions that come into contact with window glass are provided with a thin protective film which is composed of a synthetic resin whose base material is a polyolefin resin. The resin is mixed with a polyolefin resin powder or particles of various size with higher viscosity and lower fluidity than this base material. Roughened components are irregularity formed on a surface layer of the thin protective film.
Japanese Patent Application Laid-Open 2000-52780 discloses a weatherstrip in which a mold-formed part connected to an extrusion molded part is molded from a thermoplastic elastomer or soft resin to which antifriction solid particulates have been added. The ten points average roughness (Rz) of the surface of the mold-formed portion is from 1 to 50 μm.
Japanese Patent Application Laid-Open 2003-200738 discloses a weatherstrip in which a sliding part is covered with or contains a specific material so as to adjust the elastic modulus of the sliding part. In Japanese Patent Application Laid-Open 2003-200738, it is stated that dust that adheres to a sliding part contributes to the generation of noise. It is also stated that the use of materials with a low elastic modulus (soft materials) and materials with low surface energy (non-hydrophilic materials, non-moisture absorbent materials, low surface tension materials, high contact angle materials, and low SP value materials) is undesirable because dust tends to adhere to or be held by these materials, and the surface roughness of sliding parts is related to dust adhesion and retention. Also, Japanese Patent Application Laid-Open 2003-200738 states that since window glass can be scratched and sliding noise increases during the raising and lowering of window glass, it is undesirable to use a material with a high elastic modulus, Application Laid-Open 2003-200738 teaches the use of hydrophilic and moisture absorbent materials, and favorable ranges for the elastic modulus, surface tension, contact angle, SP value, and surface roughness (Rz) thereof.
Japanese Patent Publication S61-4408 discloses a weatherstrip in which the friction coefficient is lowered and wear resistance is improved. Such a weatherstrip is produced by coating with or immersion in a surface treatment agent containing silicone oil, followed by drying to form a cover layer.